Yep, I had a NASTY time finding a kit for a 4160 I just finished. Sweating bullets finding one.
You might try Mike’s Carb Parts. That’s where I found the one I needed, and the price wasn’t atrocious.
Yours is the exact example of why I just cringe doing those carbs any more. The amount of work is staggering.
I just tell them to buy new, non Holley branded carbs and tune from there. By the time you do all that work, fix all the brass so you can change it and all that, you still end up with a cast main body, base plate and metering block.
BTW, I got burned twice using 8-32 screws for the T slot restricters. I ran into a couple of builds that needed bigger than .078ish T slot restricters and that’s about all you can get with the 8-32’s, so I just do them in 10-32 now. Saves the grief of fixing it.
You have the patience of Job.